Muffler



L. G. HECTOR Feb. 7, 1939.

MUFFLER Filed July 20, 1937 2 Sheets-Shut l )NVEA/rO/Q Wmmmm m ,rne earet. 7,. 1939 PAT-Eur OFFICE MUFFLER Luther Grant Hecton Buflalo, N. Y., assign: to guflalo-Pressed Steel Company, Inc., Buflalo,

Application July 20, isszseriai No. 154,624

15 Claims.

This invention relates to improvements in mufllers or silencers for use in connection with the silencing of the exhaust of internal combustion engines.

, In my copending application Serial No. 137,686 filed April 19, 1937, I have disclosed a muiller of the reverseiiow type in which is provided a device for doubling-the pressure pulsations discharged into a mufller by an engine, and this is 3 arranged with a muflier housing of relatively large diameter which provides a relatively large chamber extending about the inlet anddischarge conduits and in which sound waves of low frequency are silenced after discharge of" the same from the pulsation doubling device, and in this muilier the discharge conduit is provided with a high frequency-acoustic train.- In some installations it is more desirable to employ a mufller of smaller diameter and greater length, so that a large chamber extending about the inlet and discharge conduits for silencing low frequency sound waves cannot be provided.

One of the objects of this invention is to provide a muiller in which a pressure pulsation doubling device and a. low frequency acoustic train may be incorporated in a muffler of relatively small diameter and in which a low frequency resonator chamber is provided for silencing low 9 frequency sound waves.

Another object of this invention is to provide a muffler with a pulse doubling device at the inlet end thereof and having low and high frequency resonator chambers located in another portion 5 of the muflier arranged rearwardly of the pulse doubling device.

It is also 'an object of this invention to provide a muiller of this kind with flow passages of improved construction for conducting the gases from thepulse doubling device to a discharge duct. having resonator chambers associated therewith. Another object of the invention is to provide a muffler which is divided by means of a transverse partition into two parts, one of .5 which contains the pulse doubling device and the other of which contains the resonator chambers.

Further objects of this invention will appear fromthe following description and claims.

In the accompanying drawings:

i0 Fig. 1 is a longitudinal sectional central view of a muffler embodying this invention.

Figs. 2 and 3- are transverse sections thereof, on lines 2-4 and 33 respectively of Fig. 1, on an enlarged scale.

35 Figs. 4 and 5 are transverse sectional views of muiiiers respectively. on lines 44, Fig. 6, and 5-5, Fig. 8.

Figs. 6, 7 and 8 are fragmentary longitudinal sectional views of mufilers provided With pressure pulse doubling devices of modified constructions.

Each of the several mufflers shown in this application is provided with an outer housing which may be of any suitable or desired construction, those shown being provided with an outer 10 imperforate cylindrical shell A having at one end thereof an inlet head B provided with an outwardly extending flanged portion forming an inlet duct 13 to which the usual exhaust pipe from an engine may be attached. The other end 15 of the shell A, as shown in Fig. 1, may be closed by means of a head C having formed thereon a discharge duct c to which'the usual tail pipe may be secured.

Referring to the mufiler shown in Figs. 1 to 3, an inlet conduit I0 is provided, one end of which is suitably secured to the inlet head B to receive gases entering the mufiier. For example, the conduit l0 may telescope within the inlet duct b and may be welded or otherwise secured thereto. The inlet duct is provided with an opening in the wall thereof, which may be in the form of a group of perforations ll of any suitable type arranged adjacent to the gas receiving end of the conduit l0. These apertures or perforations I i may, for example, be formed by providing slits in the conduit II! which extend lengthwise thereof and the metal at one side of each slit may be pressed outwardly to form louvers l2, Fig. 2, which deflect gases discharged through the opening I! in a more or less tangential direction with reference to the conduit It).

In order to provide for the doubling of the pressure pulsations entering the muffler from the exhaust pipe of the engine, the conduit l0 terminates in a substantially closed chamber located beyond or rearwardly of the discharge openings or perforations ll, so that when a gas pressure pulsation enters the conduit ill, a portion of each pressure pulsation will pass outwardly through the opening or perforations II and another portion will be carried by its momentum past the perforations l l and through the open end of the conduit l0 into the substantially closed chamber in which this portion of the pressure pulsation is reversed so that it flows back in the conduit in to theopening or perforations II and discharges through the same after and out 91 phase with that portion of the pressure pulsation which has already passed through the perforations H.

Any suitable means may be employed for constructing a substantially 'closed chamber of this type, and in the construction illustrated, I provide an intermediate shell i5 which is supported from the conduit ID by means of a transverse wall or baflle Hi. The rear end of the intermediate shell l5 may be closed in any suitable or desired manner, for example, by means of a cap or bafiie ll, so that a substantially closed chamber I8 is formed in an enclosure comprising the baflie IS, the cap I! and the portion of the intermediate shell l5 connecting this baffle and cap. An enclosure formed in any other manner may, of course, be employed if desired. The enclosure may form a chamber which is entirely closed except for the entrance provided by the inner conduit ID, or if desired, to reduce natural resonance phenomena of this enclosure, a few relatively small apertures l9- may be provided, for example, in the intermediate shell i5 which should be of small enough size and number so that only a relatively small part of the gases entering the closed chamber i8 will escape through the apertures I3.

The intermediate shell IS in the particular construction shown in Fig. 1, may, if desired, or if necessary to stop shell noises resulting from the impinging of the gases discharged from the perforations H on the outer shell A, extend forwardly from the baffle I3 towardthe inlet head B of the muifler about the opening or perforations ii of the conduit I 0 and preferably the forward end of the intermediate shell i5 is secured to the housing of the muiiier by means of a shouldered ring 20, that shown having an inner shoulder welded or otherwise secured to the intermediate shell l5 and an outer shoulder secured to the outer shell A. The portion of the intermediate shell between the bafiie i6 and the ring 20 is provided with openings of any suitable form,

such for example as the louvered apertures 2| clearly shown in Fig. 2. Consequently, gases discharged through the apertures I of the inner conduit willpass through the apertures 2| of the intermediate shell into an annular space 22 between the intermediate shell l5 and the outer shell A.

The inner conduit ll! may terminate at the entrance to theclosed chamber l8, or if desired, it may extend into the same and the portion of the conduit within the closed chamber l8 may be provided lengthwise thereof with a series of openings or peforations 24. This construction permits the gas to expand more uniformly from the conduit into the closed chamber I 8 and reduces the turbulence which results from gas breaking directly out of the relatively small conduit I 0 into the relatively large pulse doubling chamber I8. This portion of the conduit in may, however, be omitted, if desired.

The gases after leaving the pulse doubling device pass rearwardly in the annular space 22. If desired to provide a support for the rear end of the intermediate shell l5, this may be done by providing the cap member I! with an outwardly extending flange portion 25 terminating in a longitudinally extending flange 26 which may engage or be secured to the outer shell A. The outwardly extending flange portion 25 is provided with openings, such for example as arcuate slots 21, see particularly Fig. 3, through which the gases may pass from the annular space 22 into a chamber 30 formed between the cap or head 'I! of the rear end of the pulse doubling chamber i8 and a transversely extending baflie 3!, that shown being of substantially semi-spherical form and being provided with a central flanged aperture 32 to which a discharge conduit 33 may be secured. The other end of this discharge conduit terminates within the duct 0 of the head C. It will be noted that the partition or baflle 3| divides the muiiier housing into two parts, one of which contains the pulse doubling device and the other part of the housing may contain other iiow equalizing or sound wave cancelling means.

The discharge conduit 33 is preferably provided with groups of perforations or openings 3d, 35, 36 and 31 which may be of any suitable form, for example, similar to the louvered perforations H in the conduit lll'. One or more of these groups of perforations are preferably enclosed by means of a suitable shell extending about the conduit 33 to form therewith high frequency resonator chambers. In the construction illustrated, an intermediate shell 40 is provided for this purpose having its end portions 4i emending inwardly into engagement with the discharge conduit 33 and the middle portion of the intermediate shell 40 also has an inwardly extending portion 42 which contacts with the discharge conduit between the groups of perforations 36 and 35. This shell 40 may, of course, be of any suitable or desired construction to form an enclosure for a portion of the discharge conduit 33 and may either be made of a single tubular shell as described, or of any other construction, such for example as the longitudinally split multi-piece shell described in the MacKenzie, Haas and Starkweather application for patent, Serial No'. 89,606 filed July 8, 1936. The intermediate shell shown forms'with the discharge conduit a high frequency acoustic train comprising:1 (ago high frequency resonator chambers 44 an The conduit 33 and intermediate shell 30 are arranged within a chamber 4'! within the muflier housing and by providing the high frequency resonator chambers adjacent to the discharge end of the conduit 33, the groups of apertures 34 and 35 will establish communication betweenthe interior of the discharge conduit 33 and the chamber 41, a portion of which extends into the space between the intermediate shell 40 and the outer shell A. This chamber, therefore, forms a low frequency resonator chamber by means of which low frequency sounds are silenced and this chamber also helps to equalize the flow of gases discharged from the muiiier in that the peaks of pressure waves may pass through 'the apertures 34 and 35 into the chamber 41 and then return through these apertures during low pressure intervals in the conduit. The arrangement shown in Fig. 1 also has the advantage that the gases and sound waves are subjected to the action of the high frequency acoustic train after they have been subjected to the action of the pulse doubling device and the low frequency resonator chamber, which results in the most effective ac tion of the high frequency chambers.

The action of the muiiler thus far described can be under certain conditions improved by introducing a resistance to the flow of gas in the discharge conduit 33. By way of example, I have illustrated in the conduit between the perforae tions 34 and 35 an annular restricting member 48, having an outer annular flange secured to the inner surface of the conduit 33 and having a sleeve portion of reduced diameter. Any other I 2,146,188 type of restriction may, of course, be employed in I place of the one shown. This restriction tends to cause the flow of gases in the conduit 33 to become more uniform. By locating the restriction 43 between the groups of perforations 34 and 35, a by-passing of a portion of the gases through the perforations 34 into the chamber 41 and then back into the conduit 33 through the perforations 35 results and gases; and sound waves taking this by-pass or circuitous route will,

of course, enter the conduit 33 out of phase with the portions of the gas pressure and sound waves which have 'passed directly through the restriction 48. This arrangement of the restriction in the conduit, consequently, equalizes the flow of gases without .any material increase in the back pressure of the muiller.

' In the operation of the muilier which has been described. an intermittent flow of gas is discharged from the engine into the.lnlet conduit I0, this flow consisting of a series of pulses of gas with high, velocities and probably possessing a peaked wave form. The number of such pressure-pulses entering the muilier depends upon the engine speed and the wave form of the pressure pulses varies with different engines, de- .pending upon suchdactors as piston displacement, operation of exhaust valves, and the like. When a series of these rather violent pressure pulses passes through the exhaust pipe and into a muiiler, itexcites masses of gases in the exhaust system into vibration and a definite prolonged.

aftereffect probably exists after a series of such pulses has passed. The muilier shown in Figs. 1 to 3 smooths out this intermittent flow into an approximately even or steady one before any of the gas is discharged to the atmosphere. This is due, in the first place, to dividing the pressure peaks or pulses into two or more parts, the first part of each pressure pulse passing outwardly through the perforations all while the pressure pulse is moving lengthwise of the conduit. Hi. The

remainder of the pressure pulse passes into the pulse doubling chamber "and most of it is then returned to the conduit HI and discharged through the perforations ll after the first part of the pressure pulse has passed through these perforations. Portions of the second part of the pressure pulse will also pass through the apertures is in the intermediate shell I5 and this. part of the pressure pulse will also be somewhat out of phase with the'two parts of the pulse which pass through the apertures 'i I. The separate parts of the pressure-pulse which will, of course, be of greatly reduced intensity as compared with the pulse originally received-by the muiiier, will then pass successively along the annular passage 22 and through the slots 21 into the chamber from which they enter into the discharge conduit 33. In this conduit, the peaks of the remaining pressure waves, as well as sound waves, pass out through the apertures 34 and 35 into the relatively large chamber 41 which acts not only. as a low frequency resonator chamber, but also as an expansion or equalizing. chamber. The restriction or diffuser 43 also serves to equalize the flow of gases through the conduit" by slightly holding 'back'the peaks of the'waves and by forcing a considerable portion of the gas to by-pass the restriction by passing out of the apertures 34 and again entering the conduit 33 through the apertures 35. Consequently, by the time the gases and sound'waves reach the portion of the conduit "enclosed in the intermediate shell 40, a relatively uniform now 01' gas has been produced so that the high frequency acoustic train formed by the resonator chambers 44 and 45 acts very eflectively upon the gases and remaining sound waves passing through the conduit 33.

In Figs. 6 to 8, I have shown the inlet portions only of muiilers of slightly modified construction. .The muflier shown in Fig. 6, for example, differs from the muiller shown in Figs.' 1 to 3 only in that the conduit 53 terminates at the baflle 5| which forms a part of the enclosure of the pulse doubling chamber 52. Otherwise the structure shown is similar to that shown in Fig. 1.

. In Fig. 7 another slightly modified form of muiller is shown, in which a short inlet conduit 55 is provided, as shown in Fig. 6, and in which an intermediate shell 58 is provided which terminates at a bafile 51 which forms a part of the enclosure" intermediate shell 60 is short and does not extend over the perforations 8! of the inlet conduit :52

of the muffler. This construction differs from the one shown in Fig. "(in that the inlet conduit has a part or extension 63 which enters into the pulse doubling chamber 54 and is provided with perforations 65 similar to the perforations 24 described in Fig. 1'.

It'will, of course, by understood that the various constructions illustrated are merely examples of muillerswhich embody my invention and it will be obvious that my invention may be embodied in other structures than those herein illus-. trated, since it is not intended to limit this invention to the constructions shown.

I claim as my invention:

1. A muiller including a housing with an inlet at one end thereof and an outlet at the opposite end, an inlet conduit and a discharge conduit connected respectively with said inlet and outlet and extending toward each other in said housing, said inlet conduit having apertures for the discharge of gases, an enclosure forming a substantially closed chamber in which the open end of said inlet conduit terminates and which is arranged rearwardly beyond said apertures, said closure being spaced from said housing to form a passage extendinglengthwise of said housing for gases discharged through said apertures, and means located rearwardly of said enclosure for conducting gases discharged from said passage into said discharge conduit.

2. n muiiler including a housing with an inlet at one end thereof and an outlet at the opposite end, an inlet conduit connected at one end to said inlet and having its other end open and having an opening in a side thereof, an enclosure arranged rearwardly beyond said opening .and forming a substantially closed chamber in which said open end terminates and in which gas pressure pulses are reversed and returned to said conduit for discharge through said opening, means for conducting gases discharged through said opening rearwardly of said housing beyond said enclosure, an acoustic filter through which said gases pass on theirjw to said outlet. 7

3. A muflier including a housing with an inlet said inlet and having its other end open and having an opening in a side thereof, an enclosure forming a substantially closed chamber in which said open end terminates and in which gas pressure pulses are reversed and returned to said conduit for discharge through said opening, means for conducting gases discharged through said opening rearwardly of said housing beyond said enclosure, a transversely extending'bafiie in said housing beyond the rear end of said en-. closure, a discharge conduit connecting said baflle and said outlet and having a perforate portion, and an intermediate shell enclosing said perforate portion of said discharge conduit and forming therewith a high frequency resonator chamber.

4. A muffler including a housing with an inlet at one end thereof and an outlet at the opposite end, an inlet conduit connected at one end to said inlet and having itsother end open and having an opening in a side thereof, an enclosure forming a substantially closed chamber in which said open end terminates and in which gas pressure pulses are reversed and returned to said conduit for discharge through said opening, means for conducting gases discharged through said opening rearwardly of said housing beyond said enclosure, a discharge conduit arranged in said housing and receiving gases at the rear of said chamber and having perforate portions, and an intermediate shell enclosing one of said perforate portions and forming therewith a high frequency resonator chamber, said other perforate portion of said discharge conduit establishing communication between the interior of said conduit and a space between said housing and the exterior of said conduit and forming a low frequency resonator chamber, said discharge conduit connecting with said outlet.

5. A mufiler including a housing with an inlet at one end thereof and an outlet at'the opposite end, an inlet conduit connected at one end to said inlet and havingits other end open and having an opening in a side thereof, an enclosure forming a substantially closed chamber in which said open end terminates and in whichgas pressure pulses are reversed and returned to said conduit for discharge through said opening, means for conductinggases discharged through said opening rearwardly of said housing beyond said enclosure, a transversely extending baflle in said housing beyond the rear end of said enclosure, a-discharge conduit arranged in said housing and having groups of perforations arranged at intervals lengthwise of said discharge conduit, and an intermediate shell arranged in spaced relation to said conduit and housing and enclosing a group of perforations arranged near the rear end of said discharge conduit, another group of perforations arranged in advance of said intermediate shell establishing communication between the interior. of said discharge conduit and a chamber formed between said housing and said'intermediate shell and conduit and forming a vlow frequency resonator chamber.

6. A mufiler including an outer housing having an inlet at one end thereof and an outlet 'at the other end thereof, an inlet conduit connected at one end with said inlet and having an opening in the wall thereof, an enclosure in which the other end of said inlet conduit terminates and which forms a substantially closed pressure pulse doubling chamber, means for conducting gas discharged from said opening rearwardly beyond the rear end of said enclosure, a

discharge conduit into which gases pass beyond ing an inlet at one end thereof and an outlet at the other end thereof, a transverse baffle in said housing dividing the interior of said housing into two parts, an enclosure arranged in the one of said parts located at the inlet end of said muffler and spaced from said housing and from said bafile, an inlet conduit connecting said inlet with said enclosure and having an opening in the wall thereof arranged between said inlet and said enclosure, a perforate discharge conduit connecting said baflie and said outlet and extending lengthwise of the other part of said housing, and sound attenuating means ,arranged in said other part.

8. A muffler including an outer housing having an inlet at one end thereof and an outlet at the other end thereof, a transversebafile in said housing dividing the interior of said housing into two parts, an enclosure arranged in theone of said parts located at the inlet end of said muffler and spaced from said housing and from said baiile, an inlet conduit connecting said inlet with said enclosure and having an opening in the wall thereof arranged between said inlet and said enclosure, and a perforate discharge conduit connecting said bafile and said outlet and forming with said other part of said mufller housing a low frequency resonator chamber.

9. A muflier including an outer housing having an inlet at one end thereof and an outlet at the other end thereof, a transverse bafiie in said housing dividing the interior of said housing into two parts, an enclosure arranged in the one of said parts located at the inlet end .of said muffier and spaced from said housing and from said bafile, an inlet conduit connecting said inlet with said enclosure and having an opening in the wall thereof arranged between said inlet and said enclosure, a perforate discharge conduit connect-- ing said bafiie and said outlet and extending lengthwise of the other part of said housing, and a shell arranged in said other part and enclosing a perforate portion of said discharge conduit and dividing said other part into high frequency and low frequency resonator chambers.

10. A muiiier including an outer housing having an inlet at one end thereof and an outlet at' the other end thereof, a transverse baflle in said housing dividing the interior of said housing into two parts, an enclosure arranged in the one of said parts located at the inlet end of said muffler and spaced from said housing and from said baflle, an inlet conduit connecting said inlet with said enclosure and having an opening in the wall thereof arranged between said inlet and said enclosure, a perforate discharge conduit connecting said baflie and said outlet and extending lengthwise of the other part of said housing, sound attenuating means arranged in said other part, and a restriction'in said discharge conduit ing dividing the interior of said housing into two parts, an enclosure arranged in the one of said parts located at the inlet end of said mufller and spaced from said housing and from said baffle,

an inlet ,conduit connecting said inlet with said enclosure and having an opening in the wall thereof arranged between said inlet and said enclosure, a discharge conduit connecting said baflie and said outlet and extending lengthwise of the other part of said housing and having groups of perforations arranged lengthwise thereof, and a restriction in said discharge conduit arranged between groups of perforations,

12. A muiller including an outer housing having an inletat one end thereof and an outlet at the other end thereof, a transverse battle in said housing dividing the interior of said housing into two parts, an enclosure arranged in the one of said parts located at the inlet end of said muffler and spaced from said housing and from said. baille, an inlet conduit connecting said inlet with said enclosure and having an opening in the wall thereof arranged between said inlet and said venclosure, a discharge conduit connecting said baffie and said outlet and extending length wise of the other part of said housing and having groups-of perforations arranged length- .Wise thereof, a restriction in said discharge conduit arranged between groups of perforations,

and an intermediate shell enclosing another group of perforations to form a high frequency resonator chamber.

' 13. A muffler including a housing with an inlet at one end thereof and an outlet at the opposite end, an inlet conduit and a discharge conduit connected respectively with said inlet and outlet and extending toward each other in said housing, said inlet conduit having apertures for the discharge of gases, an enclosure forming a substantially closed chamber in which the open end of said inlet conduit terminates, said enclosure being spaced from said housing to form a passage for gases extending lengthwise of said housing, apertures in said enclosure to reduce natural resonance 'phenomenatherein and opening into the space respectively with said inlet and outlet and extending toward each other in said housing, said inlet conduit having apertures for the discharge of gases, an enclosure forming a substantially closed chamber in which the open end of said inlet conduit terminates, said enclosure being spaced from said housing to form a passage for gases extending lengthwise of said housing, said enclosure including a shell having a portion thereof extending about said apertures of said inlet conduit to reduce shell noises and having an opening communicating with said passage, and means for conducting gases from the rear end of said passage to said discharge conduit.

15. A mufiler including a housing with an inlet at one end thereof and an outlet at the op posite end, an inlet conduit and a discharge conduit connected respectively with said inlet and outlet and extending toward each other in said housing, an enclosure forming a substantially closed chamber in which the open end of said inlet conduit terminates, said inlet conduit having a discharge opening in the wall thereof located in advance of said chamber and through which some gases pass without entering said chamber and through which other gases pass which have re-entered said inlet conduit from said chamber,

and means for conducting gases from said opening to the rear of said chamber to said discharge conduit. 

